MIG Aluminum DIY: Selecting the Right Welder, Spool Gun and Filler Wire for Success in Your Shop | MillerWelds

MIG Aluminum DIY: Selecting the Right Welder, Spool Gun and Filler Wire for Success in Your Shop

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One of the hottest trends in welding in the shop or on the farm is adding MIG aluminum capabilities to a Millermatic® all-in-one MIG welder by complementing it with a Spoolmate™ 100 or Spoolmatic® spool gun.

MIG Aluminum DIY: Selecting the Right Welder, Spool Gun and Filler Wire for Success in Your Shop

MIG welding aluminum Q&A

Spool guns improve the "feedability" of aluminum wire by locating a small, 1-lb. (4-inch diameter) spool of wire on a pistol-grip style gun. Because spool guns only need to feed the wire just a few inches before it hits the weld puddle, they eliminate the potential problems created by pushing soft aluminum wire 10 or 15 feet through a regular gun. By using a spool gun, you'll spend more time making better welds and less time cussing at a "bird nest" of wire tangled around your drive rolls.

Here are some common questions and answers that will improve your understanding of aluminum and help you make the right equipment and filler metal choice.

Q: How do I know which spool gun to use with my welder?

A: First of all, understand what spool guns are compatible with your welder or the welder you are purchasing. Spool guns are sized to match the performance of the welders they are aligned with (refer to Fig 1). If there are multiple spool guns available for your machine, then you should look at the rating and the duty cycle of each gun and purchase the one that best matches your usage requirements.

As a rule of thumb, as the duty cycle increases, the spool gun becomes more industrial and designed for heavier usage, therefore causing the price to increase.

Fig. 1 - Spool Gun/Millermatic® Welder Selection Guide

Spool Gun Choice

Aluminum Wire Diameter

Duty Cycle

Matching Welders

Spoolmate 100

.030 or .035 in.

135 amps @ 30%

Millermatic 141

Millermatic 211

Spoolmate 200

.030 or .035 in.

160 amps @ 60%

Millermatic 212 Auto-Set

Millermatic 252

Spoolmatic 15A, 30A  (15 or 30 ft. cables)

.030, .035, .047 or .062 (1/16th)

200 amps @ 100%

Millermatic 212 Auto-Set

Millermatic 252

Q: Which are the best Millermatic welders for welding aluminum in DIY, farm/ranch, general maintenance and other "occasional" welding applications?

A: In general we recommend that you purchase a welder capable of welding on 230V input power due to the properties of aluminum. Without getting too technical, a lot of energy is needed to overcome aluminum's thermal conductivity rate and melt through the aluminum oxide which forms on the outside of bare aluminum. In general, 115V welders do not have enough power to overcome these properties and lead to poor fusion while welding.

Therefore, the Millermatics we recommend are the 141, 211, 212 and 252. From here you need to pick the machine that meets your needs in regards to welding output, duty cycle, physical size and feature sets. The most popular choice is the Millermatic 211 because of its Auto-Set feature, MVP plug, small size and high output.  If it is a larger machine you are looking for, both the Millermatic 212 and 252 are great choices.

Q: Which wire diameter should I use?

A: The first place you should look is at the welding parameter chart on your machine to see what wires the machine and spool gun are designed to work with. In general thicker wires feed better, while smaller diameter wires work better on thinner material. In general, Miller recommends using either a .030 or .035 in. diameter aluminum wire for most projects around the home.

Q: So what's the difference between all those grades of aluminum?

A: The technical answer is that aluminum requires the addition of alloys to increase its strength and to add other qualities suitable for various applications . Their series numbers identifies common alloys. The good news is that when it comes to MIG welding, there are only two real choices-4043 or 5356 filler wire-and they can be used to weld a the following alloys: 3000, 4000, 5000 and 6000 series aluminum.

Q: So which wire do you use? 

A: For most DIYers, 4043 will work best. It is the easiest filler to weld with because it "burns" slower and has silicon added to aid in puddle control. Additionally, the smaller Millermatics (141 and 211) are optimized for this wire. On the other hand, if you need an aluminum weld to be a little stronger or have improved corrosion resistance, then 5356 would be the filler of choice.

It should be noted that 5356 melts considerably faster, so more skill is needed to weld with this filler material. You should also make sure that your spool gun has enough wire feed speed to keep up with the amount of 5356 filler needed when using smaller machines on thicker aluminum base material. Review the specifications for your spool gun/welder combination and compare them to the wire feed speeds noted in Fig. 2.

Fig. 2 - Typical Parameters for 4043 and 5056 Aluminum Wire

Wire Diameter

Amp Range

Wire Speed IPM


100 - 150

500 - 600


85 - 190

480 - 740


125 - 240

360 - 470


190 - 340

265 - 420

Q: Are there any special storage considerations for aluminum wire?

A: Yes-don't open a new package of wire until right before you plan to use it. Aluminum filler wire oxidizes, and this can lead to an erratic arc because oxidation adds resistance, can produce soot and can change the wire's ability to feed smoothly. Many operators have spent a great deal of time adjusting tension settings, changing contact tips or checking the shielding gas trying to fix the problem when oxidized wire caused the problem. Discard the oxidized spool and open a fresh package.